19. Down syndrome results from a mutation best described caused by during meiosi

Question

19. Down syndrome results from a mutation best described caused by during meiosis. a. Point; nondisjunction c aneuploidy; nondisjunction b. framshift crossing over d. deletion; independent assortment 20. When both strands of our DNA are being replicated, one strand is leading, while the other contains This is because DNA polymerase works a. Okazaki fragments; only in a 5-3' direction c. Also leading: in both directions b. Okazaki fragments; only in a 3-5' direction d. Also leading: by adding new nucleotides to the 5' end 21. Nucleotides are made of A. Only Sugar and phosphate group C. Only Nitrogenous base B. Only Sugar and nitrogenous base D. Sugar, phosphate group and a nitrogenous base 22. When the ends of chromosomes are replicated, we need the help ofbecause of the lagging strand problem. A. reverse transcriptase 8. telomerase C helicase D. RNA polymerase eDNA of an organism has guanine (G) as 30% of its bases what percentage of its bases would be adenine an A 10% 23, Th B, 20% C.30% D, 40% 24. Which is the following is true about transcription? A. Both strands of DNA are used as template to make mRNA. B.Only the 5-3' strand of DNA is used as a template C. Only the 3'-5' strand of DNA is used as template D. Telomerase is necessary to complete the mRNA. 25. When DNA has to be unzipped for replication or transcription, bonds need to be broken. A covalent B. ionic C. phosphodiester D. hydrogen

Explanation / Answer

19. Down syndrome results from the trisomy of chromosome 21 the reason behind trisomy is the non-disjunction event during meiosis. Thus, option C is correct.

20. DNA polymerase requires a free 3' OH group for synthesis of new strand. Thus, DNA polymerase moves along the template strand in a 3'-5' direction making the new daughter strand in 5’-3’ direction. So, option a and b are both correct but depend on the strand under consideration, if we consider parent strand strand for the direction b will be correct. And if we will consider the direction of daughter strand option a is correct. So, option b is correct for the direction of DNA pol on template strand.

21. Nucleotide is made up a nitrogen-containing base, a five-carbon sugar, and a phosphate group. So option D is the answer.

22. The ends of linear chromosomes extended with a specialized enzyme called telomerase which is a type of reverse transcriptase which is having its own RNA template for DNA synthesis. So, option b is answer.

23. 30% of G will binds to 30% of C which adds up to 60%. The remaining 40% will be the equal percentage of A and T according to Chargaff rule. So,20% of A will be the answer (option B).

24. only the template strand is used as a template for RNA synthesis in 3’to 5’ orientation by giving the mRNA of 5’to3’. So, option C is the answer.

25. The hydrogen bonds needs to be broken for replication or transcription. option D is answer.

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